Förster resonance energy transfer (FRET) is a mechanism describing an energy transfer between two chromophores. A donor chromophore, initially in its electronic excited state, may transfer energy to an acceptor chromophore in proximity through nonradiative dipole-dipole coupling. In fluorescence microscopy, fluorescence confocal laser scanning microscopy, as well as in molecular biology, FRET is a useful tool to quantify molecular dynamics in biophysics and biochemistry, such as protein-protein interactions, protein-DNA interactions, and protein conformational changes.
Some studies using FRET have been conducted to determine stoichiometry of some plasma membrane proteins. However, detection of changes in oligomer stoichiometry caused by pharmacological reagents or endogenous molecular chaperones, or the simultaneous detection of multiple stoichiometries expressed in the same region of interest still remains a challenge.